Serum elafin levels in patients with IgA vasculitis: a prospective case-control study.

Objectives: Immunoglobulin A vasculitis (IgAV) is a small-vessel vasculitis characterized by perivascular IgA deposition and neutrophil activation. Elafin, an anti-inflammatory and anti-protease protein expressed by epithelial and select immune cells, may play a role in modulating vascular inflammation. We evaluated serum elafin levels in pediatric patients with IgAV during active stage and remission, and investigated their associations with disease activity, organ involvement, and systemic inflammatory markers.

Methods: This single-center prospective case-control study included 51 pediatric patients diagnosed with IgAV and 54 age- and sex-matched healthy controls. Paired data were obtained from the same IgAV patients during the remission phase, allowing intra-individual comparisons. Serum elafin levels were quantified using enzyme-linked immunosorbent assay (ELISA). Inflammatory parameters, including complete blood counts, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR), were assessed in all participants.

Results: Serum elafin levels were significantly elevated in patients with IgAV (45.43 ± 11.11 ng/dL; range: 34.02-69.28) compared to healthy controls (27.44 ± 12.66 ng/dL; range: 0.01-41.84) (p < 0.001), with the highest concentrations observed during active disease stage (p < 0.001). Patients with visceral involvement (gastrointestinal, renal, or scrotal) exhibited significantly higher elafin levels (p < 0.05), whereas no significant association was found with isolated skin or joint involvement. Serum elafin levels demonstrated positive correlations with the ESR (p = 0.001, r = 0.418), CRP (p < 0.001, r = 0.547), neutrophil-to-lymphocyte ratio (p = 0.002, r = 0.355), and systemic immune-inflammation index (p = 0.003, r = 0.347). Receiver operating characteristic curve analysis identified an optimal serum elafin cut-off value of 35.38 ng/dL for distinguishing active IgAV, yielding a sensitivity of 86.2% and specificity of 77.8%.

Conclusion: Serum elafin levels were significantly elevated during the active stage of IgAV and may serve as a potential biomarker for disease activity, particularly in patients with visceral involvement.